Thermostatic switch plug



Oct. 23, 1928.

C. ARNESEN THERMOSTATIC SWITQH PLUG Filed March 24, 1926 LEFHQ 12Patented Oct. 23, .1928.

UNITED STATES CHARLOTTE ABNESEN, (IF-CHICAGO, ILLINOIS.

THEBMOS'I'ATIC SWITCH PLUG.

Application filed March 24, 1926. Serial No. 96,921.

The invention has general reference to plugs of the type employed inconnection with electrical appliances, and more especially heatingappliances for efl'ecting a detachable connection between the applianceand a suitable current conductor.

The primary object of my invention is to provide a plug of the generalcharacter stated, which embodies in itself a switch of novel andadvantageous construction such that it is adapted to be operatedthermostatically to open the circuit when the temperature of theappliance to which its attached reaches a predetermined maximum, andthus prevent injury to the appliance and insure against fire hazards orother damage.

A general object is to provide a plug with a thermostatically operatedswitch mechanism which is simple in construction, compact in arrangementand efiectual in its operation, to the end that a practical controllingunit may be produced at a relatively low cost for use on existingelectrical appliances and equipment.

In the accompanying drawings wherein I have illustrated my invention ina preferred form, Figure 1 is a side elevational view of my improvedplug applied to an electric iron, the latter being selected as exemplarymerely of the appliances and electrical equipment witlil which myinvention is adapted to be use Fig. 2 is a fragmentary plan view of onesection of the plug in which the switch is mounted.

Fig. 3 is a longitudinal sectional view taken approximately in the planeof line 3 -3 of Fig. 2, but showing the two sections of the plug inassembled relation with the switch mechanism therein.

Fig. 4 is a fragmentary longitudinal sectional. view on an enlargedscale taken substantially in the same plane as Fig. 3, but showing theparts in a diflerent relation.

Referring now to the drawings, 7 designates generally my improved plugapplied to an electric flat iron 8 and serving as a connection betweenthe iron and a cord 9 which may be connected with a suitable source ofcurrent supply, the plug being detachably applied to standard terminalposts or plus 10.

The plug comprises asherein shown two substantially similar sections,namely, a base section 11 and a cover section 12. Each of the sectionsis formed from a substantially flat piece of material such as bakeliteor other insulating substance and the adjacent faces of the two sectionsare cut away so that when the two sections are secured together an innerclosed chamber 13 is provided to receive the switch and associatedparts.

Leading downwardly and outwardly from the lower end of the chamber 13are a pair of spaced parallel passages 14 in which socket members 15 and15" are entered so as to be capable of receiving standard terminal posts10. At the opposite or upper end of the chamber 13 an enlarged opening16 is formed for the reception of the usual coiled wire guide member 17through which the conduct/or 9 passes for entry into the plug. It willbe understood that the socket members 15 may be of any suitable orprefered construction, and the same is true of the flexible wire guide17. The two sections of the casing may also be secured together in theusual way as by means of screws 18.

In the chamber 13, at one side thereof, I

provide a combined supporting and conducting unit comprising a plate 19which in the preferred embodiment is adapted-to lie fiat upon the sidewall of the chamber and is rigidly connected with one section of thesocket member 15. Thus the plate is bent or offset upwardly slightly asindicated at 20 (Fig. 3) approximately into the plane of the section ofthe socket member to which it .is secured as by means of a screw.Similarly the opposite end of the plate 19 has formed integral therewitha terminal lug 21 ofiset upwardly from the face of the plate 19 andhaving one of the wires of the conductor 17 connected thereto as at 22.

One section of the other socket member 15' has rigidly secured thereto aresilient or spring arm 23 which extends upwardly in the plug throughthe chamber 13 to a point near the upper end of the chamber. This arm 23as shown in Fig. 2 is spaced laterally from the plate 19, being arrangedin the present instance so as to lie closely adjacent to the wall of thechamber 13 opposite the plate 19. 24 is a stationary contact arm at theupper end of the chamber 13 with which the upper end of the movable armis adapted to contact. This stationary contact arm 24 is formed integral with an upwardly offset terminal lug 25 to which the other wireof the conductor 17 may be secured as by means of a screw 26.

Projecting inwardly from one edge of the plate 19 and extendinglongitudinally thereof is a flange 27 constituting a supporting brackctfor the switchoperating mechanism. Said mechanism comprises an arm 28pivoted on the upper end of the flange 27 as at 29. The other end ofthis arm 28 is bent so as to carry an insulated stud 30 which, on theone hand is adapted to engage the movable contact arm 23 near the upperend of the latter, and on the other hand is adapted to be engaged by theinner end of a push button 31 slidable through an aperture 32in thecover section of the plug. The stud 30 is preferably made from a shortpiece of insulating tubing such as bakelite and serves to prevent ashort circuit between the spring contact arm 23 and the plate 19. Also,the button 31 is preferably made of insulating material such asbakelite, and its lower end may be enlarged to provide a bearing plate33. Inward pressure upon the button 31 is adapted to force the springcontact arm 23 into engagement with the stationary contact 24 and thusclose the circuit.

The circuit is adapted to be held closed releasably by a latch devicecomprising an arm 34 pivoted at its lower end at 35 on the flange 27.Midway between its ends this arm 34 has a stop lug 36 which is movablein the swinging movements of the arm into and out of the path of a stopshoulder 37 formed on the arm 28. This shoulder'37 is formed at the endof an arcuate segment 38 formed integral with the arm28 and uponwhichthe stop lug 36 is adapted to slide in the movement of the stud 30 toforce the movable contact arm 23 against the stationary contact '24. Thearrangement is such that when thestud is forced;

by the push button 31 to carry the arm 23 into firm engagement with thecontact 24, the stop lug 36 will engage below the shoulder 37. Suchmovement of the stop lug relative to the shoulder 37 is eifeet'ed by aleaf spring.

39 the lower end of which may be secured upon a lug 39* on the flange 27and the upper end of which engages with a lug 40 on the arm 34 spaced ashort distance from the pivotal axis 35 of said arm.

The upper portion of the arm 34 curves from one side of the chamber 13to the other, and its extreme upper end occupies a position adjacent theinner end of an actuator, herein in the form of a'push button 41slidable in a hole in the base section of the casing. The inner end ofthis actuator has a head 42 with an annular groove therein to receivethe bifurcated forward end of a thermostatic element in the form of anelongated metallic strip 43 (Fig. 2). This strip extends generallylongitudinally of the chamber 13 and its lower end is secured as at 44to the plate 19. The latter, it will be remembered, is rigid with onesection of the terminal socket member 15, so that heat from the iron orother appliances is conducted through the terminal post of pin and thesocket member to the thermostatic element.

It will be seen that the lever arm 34 is adapted to be operated eithermanually by means of the actuator 41 or automatically by means of thethermostatic element 43. In this connection, it is noted that the leafspring 39 is made from a thin strip of resilient material so as to exertonly a very slight pressure upon the arm 34 whereby to hold the arm inopera tive relation to the stud-carrying arm 28. In other words, thestrength of the spring 39 is suflicient only to insure the operation ofthe latch device 36, 37.

In the use of my improved plug, the switch is operated manually to closethe circuit by depressing the button 31 to carry, through the medium ofthe stud 30, the spring contact arm23 into engagement with thestationary contact 24. In this movement of the stud 30 the arm 28 isswung until the stop lug 36, riding on the curved surface 38, is free tosnap into position beneath the shoulder 37 under the-influence of thespring 39. Preferably the parts are so arranged that after the free endof the movable contact arm 23 engages the stationary contact v24,continued pressure must be applied to the push button 31 so as to bendthe arm 23 slightly before the latch device consisting of the stop lug36 and the shoulder 37 will interengage.

- If it is desired to open the circuit manually this may be done byoperating the push button 41 so as to swing the arm 34 and disengage thelatch device. When this occurs the contact arm 23, because of itsresiliency, snaps away from the stationary-contact 24 and interrupts thecircuit.

To prevent the temperature of the iron or other appliance from becomingtoo high for safety, the circuit will be broken through the operation ofthe thermostatic element also acting on the lever arm 34 to disengage.the latch device, the arrangement being such that as the temperature ofthe heat conducting plate 19 increases the thermostatic element willbend upwardly at its free end as is well understood in the art, andthrough the medium of the push button or actuator 41 swing the lever 34.Because of the arrangement employed, the relatively small force whichthe thermostatic element is capable of exerting, is adapted to disengagethe latch device.

Whether the latch device is disengaged manually or theremostatically, itwill be obvious that by reason of the employment of the two pivotedmembers 28 and 34 the switch contacts are held in closed relation duringthe time that the latch is being operated to efiect disengagement. Thisis especially advantageous in the case of the disengagement eflected bythe thermostatic element, for, as will be understood, this operation mayrequire considerable time and if the movable switch contacts werepermitted to move with the thermostatic element an arcing of currentacross the. contacts would occur. The arrangement employed insures asharp breaking of the circuit, the pivoted member 28 re mainingstationary until complete disengagement of the latch device has beeneffected by the movement of the member 34.

To hasten the cooling of the thermostatic element after the current hasbeen disrupted, a small venting aperture may be provided in the casing,preferably adjacent the lower end of the thermostatic element.

It will be seen that I have provided a controlling unit which is simpleand inexpensive, and capable of being readily applied to existingelectrical appliances and other equipment. The device is especiallyapplicable to electric flat irons because of combined thermostatic andmanual control. In the case of such appliances varying temperatures arerequired depending upon the nature of the work being done. For example,in ironing thin 01' delicate materials a relatively low temperature isneeded; whereas for heavier materials a substantially higher temperatureis required. In the case of prior control devices, the practice has beento fix the temperature at which the current will be interrupted inaccordance with the maximum that can be used on the lighter or thinnermaterials, in order to avoid injury thereto, and it is impossible -toincrease the temperature of the iron above that fixed point even thoughthat may be necessary for eflicient work on heavier materials. I haveovercome this objection to prior devices by employing a switch which isboth manually and thermostatically operable. This renders it possible tofix the point at which the current is cut'ofi at the maximum temperaturerequired for eflicient work in any case, the interruption of the currentat any point below this maximum being under the control of the operator.The maximum temperature permitted, it will be understood, is such as toinsureagainst fire hazards due to carelessness, neglect or conditionsbeyond the control of the operator.

I claim as my invention:

1. In a plug of the character desired, a switch device comprising a pairof relatively movable contact members normally tending to move intospaced relation,a bracket having an arm pivoted thereto, a push buttonfor swinging said arm, a second arm also pivoted on said bracket, alatch device operatively associated with said arms and adaptedreleasably to hold the first arm against movement and the contactmembers together, and means for moving the second arm to release saidlatch device.

2. In a plug of the character described,

a switch device comprising a pair of relative- 1y movable contactmembers normally tending to move into spaced relation, a bracket havingan arm pivoted thereto, a push button for swinging said arm, a secondarm also pivoted on said bracket and movable relative to the first arm,a latch device operatively associated with said arms and adaptedreleasably to hold the contact members together, and a thermostaticmember adapted to be subjected to the heat of the appliance and operableat a predetermined temperature to move the second arm whereby to actuatethe latch device.

3. In a plug of the character described, the combination of a casinghavinga plate extending longitudinally therethrough so as to constitutean electrical conductor and also adapted to be subjected to the heat ofan electrical heating appliance to which the plug may be applied, astationary contact member and a movable contact member, means forreleasably holding said contact members together including a pair ofpivoted interlocking arms and a thermostatic element secured to saidplate and arranged to move one of said arms whereby to operate the lastmentioned means. 4. In a device of the character described, thecombination of a pair of relatively movable switch contacts, means forreleasably holding said contacts in closed relation including a leverpivoted at one end, and a latch device operatively associated with saidlever at a point adjacent its pivoted end, and thermostatically actuatedmeans for engaging said lever near its free end whereby to disengagesaid latch device.

5. In a device of the character described, the combination of a pair ofrelatively movable switch contacts, means for releasably holding saidcontacts in closed relation including a le er and a latch deviceoperatively associated with thelever at a point adjacent its fulcrum,and a thermostatic element adapted to engage said lever at a pointremote from its fulcrum to move it and thereby disengage the latchdevice. 7

6. In a device of the character described, the combination of a pair ofrelatively movable switch contacts, means for releasably holding saidcontacts in closed relation including a pivoted member of substantiallength, a second pivoted member operatively associated with one of saidswitch contacts to move it, said two members liavingmeans adapted tointerlock at a point near the pivotal axis of the first member andoperating to hold said contacts in closed relation, manually operablemeans for moving said second member, and means for moving the firstmember to disengage said interlocking means.

lllll 7 In a device of the character described,

the combination of a stationary switch contact, a movable switch contactin the form of a resilient arm, a member pivoted at one holding saidcontacts in closed relation ineluding a lever movable independently ofsaid pivoted member and a releasable latch acting between said memberand said lever.

8. In a device of the character described,

the combination of a stationary switch contact, a movable switch contactin the form of a resilient arm, a member pivoted at one end and having apart at its other end adapted to engage with said arm, a manuallyoperable device for moving said member whereby to move the movablecontact into engagement with the stationary contact, and means forholding said contacts in closed relation including a latch device havinga pair of interlocking parts and a lever carrying one of said parts.

9. In a device of the character described, the combination of astationary switch contact, a movable switch contact in the form of aresilient arm, a member pivoted at one end and having a part at itsother end adapted to engage with said arm, a manually operable devicefor moving said member whereby to move the movable contact intoengagement with the stationary contact, and means for holding saidcontacts in closed relation including a latch device having a pair ofinterlocking parts and a lever carrying one of said parts, said leverbeing of substantial length and the said part carried thereby beinglocated adjacent the fulcrum of the lever.

10. In a device of the character described, the combination of a casingproviding opposed walls, a pair of switch contacts mount ed for relativemovement in the casing, a member pivoted in the casing and having a partadapted to engage with one of said contacts, a ush button operatingthrough one wall of t 1e casing and adapted to actuate said member inone direction, a latch device operating upon said men ber whereby tohold said contacts in closed relation,'a lever for operating said latchdevice, a thermostatic device for moving said lever, and a push buttonoperable through the opposite wall of the casing to disengage said latchdevice.

- 11. In a device of the character described, the combination of acasing providing opposed walls, a pair of switch contacts mounted forrelative movement in the casing, a member pivoted in the casing .andhaving a part adapted to engage with one of said contacts, a push buttonoperating-through one wall of the casing and adapted to actuate saidmember in one direction, a latch device operating upon said memberwhereby to hold said con tacts in closed relation, and a second pushbutton operable through the opposite wall of the casing to disengagesaid-latch device,

said latch device including a lever having a detent arranged tointerlock with said pivoted member, and the second push button beingadapted to engage said lever to release the latch device.

12. In a device of the character described, the combination of a casing,a pair of switch contacts mounted for relative movement in the casing,means for manually moving one of said contacts into closed relation withthe other contact, means for releasably holding said contacts in closedrelation including a member pivotally mounted near one end of the casingand extending to the other end of the casing, and a thermostatic elementhaving one end secured near the end of the casing adjacent the pivotedend of said lever and its other end operatively associated with the freeend of said lever.

13. In a device of the character described, the combination of a casing,a pair of switch contacts mounted for relative movement in the casing, aplate secured in the casing and having an upstanding flange, means forcontrolling said contacts including a pair of members pivoted on saidflange and having means releasably holding them against relativemovement, one of said members acting when thus held to hold the switchcontacts in closed relation, and means for moving the other one of themembers to release said holding means.

14:. In a device of the character described, the combination of acasing, a pair of switch contacts mounted for relative movement in thecasing, a plate secured in the casing and having an upstanding flange,means for controlling said contacts including a pair of members pivotedon said flange and having means releasably holding them against relativemovement, one of said members acting when thus held to hold the switchcontacts in closed relation, and a thermostatic element in the form of aflat strip secured at one end to said plate and its other end arrangedto engage with the other one of said members.

15. A switch plug comprising, in combination, a casing of insulatingmaterial, a metallic bracket in said casing, a pair of socket membersone of which is thermally connected with said bracket, a pair ofcontacts normally tending to move into spaced or open relation,

an arm pivoted on said bracket, a button projecting from the casing andoperatively associated with said arm to close said contacts, a latchdevice operable to hold said contacts closed, a second arm also pivotedon sa d bracket and operable while the first arm 1s stationary todisengage said latch device, said second arm also having a buttonprojecting through the casing, and temperature responsive meansincluding a thermal element secured to said bracket and operable todisengage the latch device.

16. ,A switch plug comprising, in combinasaid manual means isoperatively associated,

' a thermostatic element for disengaging the latch device, and manuallyoperable means also adapted to disengage the latch device, the lastmentioned means including a pivoted member movable independently of thefirst 10v mentioned pivoted member.

In testimony whereof, I have hereunto aflixed my signature.

CHARLOTTE ARNESEN.

